Optical transmission module for achieving an optimum optical connection and useful for high density mounting

ABSTRACT

An optical transmission module or an optical module has a receptacle attached adjacent to an optical component module or package, and a plug configured to connect vertically with the receptacle from above the module. The outer peripheral shape of the housing is designed to fit within an area of the receptacle that faces upwardly to receive the plug in an insertion direction extending vertically downwardly. In the housing of the plug, a ferrule is attached to an end of an optical fiber and a sleeve covers the optical fiber and the ferrule. A knob is used for moving the optical fiber, the sleeve and the ferrule in the lightwave propagation direction, which is transverse to the plug insertion direction. Before connecting the plug, the knob is retracted to pull the ferrule and the sleeve within the plug housing. This prevents contact of the ferrule in the plug with a mating ferrule in the optical component package that extends into the receptacle in optical alignment therewith when the plug is seated within the receptacle. The ferrule in the optical component package is connected to an optical component via another optical fiber. Upon completion of the insertion of the plug, the knob is released and the force of a spring holds the ferrules in contact with on another with sufficient force to maintain a detachable optical connection.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical transmission module or anoptical module. In particular, the invention relates to an opticaltransmission module or an optical module having an optical connectormechanism.

2. Description of the Related Art

Optical communications systems for communications networks having alarge capacity of data transmission have been developed for wide spreaduse and will continue to be further developed in the future consideringthe demand for multimedia in society.

Communications systems include optical transmission modules or opticalmodules that are placed in an optical network unit of an opticaltransmission network. However, since such optical transmission modulesor optical modules are expensive, it is desirable to reduce their cost.One of the reasons why such modules are so expensive is that theconventional optical transmission modules or optical modules are pigtailtype modules which cannot be readily detached from the optical fiber.Once the optical fiber is attached to the optical transmission module oroptical module, it is difficult to perform reflow soldering and tohandle the optical fiber itself.

Optical transmission modules or optical modules in which the opticalfiber is capable of being detached have been proposed. For instance, asurface mountable optical module having a simple type optical connectorstructure to which an optical fiber is able to be attached is describedin IEEE Transactions on Components, Packaging, and ManufacturingTechnology-Part B, Vol. 19. No. 3, pp. 524-531, August 1996. This simpletype of optical connector includes an optical connector pigtail for theoptical fiber and. a receptacle that receives the connector positionedat the edge of the optical module.

By using an optical module having an optical connector structure fromwhich the optical fiber connector can be detached, it becomes relativelysimple to perform reflow soldering and handling of the optical module,followed by connection of the optical fiber to the module. The cost ofthe optical module is also reduced by employing such type of opticalconnector structure.

SUMMARY OF THE INVENTION

However, in the conventional art, it is necessary to provide sufficientspace along the surface of the mounting board adjacent to the receptacleat the edge of the optical module for connecting the optical fiberconnector. The reason the space is provided is because the direction ofmovement of the connector with respect to the receptacle of the moduleis in parallel with the mounting board surface of the optical module.Since it is necessary to maintain such a space adjacent the module forthe connector, other chip components cannot be mounted in the space.Therefore, in the conventional art, a problem arises in that it isdifficult to mount several kinds of components on a board in order toachieve high density of the components or to mount the optical module ona central portion of the mounting board.

Accordingly, an object of the present invention is to solve the problemof the conventional art by providing an optical transmission module oroptical module suitable for high density mounting.

Another object of the present invention is to provide an opticaltransmission module or optical module having an optical active componentwith a receptacle prepared at one edge of the optical module forreceiving a plug to which an optical fiber is connected. The connectionof the receptacle and the plug can be made in a detachable manner fromabove the module so that the plug is optically coupled with the opticalmodule active component after mounting of the module on a mounting boardor surface.

The optical components mounted in the optical module include an opticalfiber, an optical waveguide, an optical device, etc. The housing of themodule has a receptacle that is shaped to mechanically fit with thehousing of the plug. Further, the plug includes a mechanism to move theoptical fiber back and forth with respect to the plug.

In a circuit board having the optical transmission module or opticalmodule of the invention mounted thereon, a plurality of electroniccomponents can be placed peripherally around the optical transmissionmodule or optical module, and it is still possible to detach the plugfrom the receptacle.

An optical connector relating to the present invention includes areceptacle having a first optical fiber extending to an edge of theoptical module with a ferrule and a plug to which a second optical fiberis connected that is shaped to fit within with the receptacle in adetachable manner from above the receptacle. In particular, the plug isconfigured to hold the second optical fiber for optically connecting itwith the first optical fiber. The plug preferably includes a mechanismfor moving the second optical fiber with respect to the plug in thedirection of lightwave propagation of the module. Such a mechanism mayinclude a knob attached to a ferrule to which the second optical fiberis fixed and a resilient member (e.g., a spring) biasing the movement ofthe knob toward a position in which the ferrule of the plug engages aferrule of the module.

Additionally, the present invention provides a method for connecting anoptical connector for an optical fiber to a component. The methodinvolves the use of a connector mounted to an optical fiber, such as aplug. The plug has a configuration or shape that interfits with thereceptacle from above the module when the plug is pushed or placed inthe receptacle. The optical fiber passes through the housing of the plugto the outside of the housing and is optically coupled to the tip of thefirst optical fiber installed in the receptacle after the plug andreceptacle have been fit together. The method also provides fordetaching the optical connector or plug from the receptacle by firstwithdrawing the ferrule of the plug from optical engagement with theferrule of the receptable and then detaching the plug from the housingof the receptacle by removing it therefrom in an upper direction.

Through the aforementioned, a high density mounting of the opticaltransmission module or optical module can be realized.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the present invention are described below inconjunction with the figures, in which:

FIG. 1 shows a diagram of an embodiment of an optical transmissionmodule or an optical module of the present invention;

FIG. 2A shows a sectional diagram of the module taken along line A—A′shown in FIG. 1, before inserting a plug side of housing 11 into areceptacle side of housing 18;

FIG. 2B shows a sectional diagram of the module taken along line A—A′shown in FIG. 1, where a plug side of housing 11 is connected with areceptacle side of housing 18;

FIG. 2C shows a sectional diagram of the module taken along line A—A′shown in FIG. 1, with the plug and receptacle being optically connected;and

FIG. 3 shows a circuit diagram of a circuit board with an opticaltransmission module or an optical module of the present inventionmounted thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A description will be given of the present invention by reference to theaccompanying drawings.

FIG. 1 shows an optical transmission module or an optical module 23 ofthe present invention that includes an optical component module with areceptacle 24 at one side or end of the module 23 and a plug 25configured to receive the receptacle 24. The receptacle 24 has apartially open top or area facing upwardly that is open to receive theplug as shown by the projection lines in FIG. 1, which shows thepreferred embodiment of the optical connector of the present invention.

As shown in FIG. 1, plug 25 is inserted into the receptacle 24 fromabove the module or otherwise lowered downwardly into the receptaclefrom an upper direction. The plug 25 is housed in a housing structure 11that has a cross-shaped or t-shaped guidance structure that mates withthe shape of the upwardly facing open area of the receptacle 24. In thehousing 11 of the plug, a ferrule 17 is attached to the end of anoptical fiber 15 for establishing an optical connection. Optical fiber15 exists the housing 11 in a longitudinal direction generally extendingin alignment with the lightwave propagation direction or otherwise in adirection transverse to that of the insertion direction of the plug 25into the receptacle 24. A sleeve 6 prevents optical misalignment andcovers the optical fiber 15 and the ferrule 17.

A knob 13 that is part of a retraction mechanism in plug 25 enables theoptical fiber 15 to be moved within the housing 11 in conjunction withthe sleeve 16 and the ferrule 17 in the lightwave propagation direction.A knob guidance groove 12 is provided for guiding the movement of andholding the knob 13 in the retracted position. The knob 13 is secured toferrule 17. A spring 14 pushes against knob 13 to bias the knob, opticalfiber 15 and ferrule 17 in the lightwave propagation direction or towardthe optical component in the optical component module. The spring, as tobe explained hereinafter, provides sufficient force to establish thecontact pressure necessary to achieve optical connection between theferrule 17 of the plug 25 and a ferrule 22 of the optical componentmodule.

The outer periphery of the plug housing 11 is dimensioned and shaped tofit into the upwardly facing open area of the receptacle. At the time ofinsertion, the knob 13 is pulled back along knob guidance groove 12.Therefore, the sleeve 16 is retracted and stored within the housing 11so as to avoid contact with the housing 18 at the time of insertion.

The receptacle 24 has a housing structure 18. Receptacle 24 ispositioned at one end of a side of the module 23, adjacent to an opticalcomponent module or package 19. A V-grooved silicon optical bench 20 isplaced in the package 19 along with a combined optical fiber withferrule 22 that is fixed on the substrate 20. An optical device 21 isoptically coupled with the optical fiber with ferrule component 22 andis also mounted on the substrate 20. Although the optical device 21 is,according to a preferred embodiment of the present invention, asemiconductor laser diode, other optical devices, such as a photo-diodemay be used.

FIGS. 2A through 2C show a sectional view of the optical module 23 takenalong line A—A′ shown in FIG. 1. FIG. 2A shows the plug 25 andreceptacle 24 just before inserting the plug into the receptacle. At thetime of insertion, a knob 13 is pulled back against the force of thespring (to the left side of the figure, as shown) and is positionedwithin knob guidance groove 12 of FIG. 1. In this position, sleeve 16 isstored completely or fixed within housing 11 and plug 25 is able to bepushed down vertically into receptacle 24 through the upwardly facingopen area or top of the receptacle to become seated within thereceptacle. That is, the plug housing 11 mates with receptacle 25 whenpushed into the receptacle in an insertion direction extendingtransverse to the direction of the lightwave propagation direction ofthe optical connection to be established between optical fiber 15 andthe ferrule and optical fiber component 22.

FIG. 2B shows the positioning of plug housing 11 within the receptaclehousing 18. The insertion of the plug housing 11 into the receptacle isstopped by a bottom wall of the receptacle housing 18 and a height offerrule 17 is fixed correspondingly. After the plug 25 has been seatedinto the receptacle 24, knob 13 is released by bringing it back to anoriginal position along the knob guidance groove 12 in which the sleeve16 is biased toward package 23 by spring 14.

FIG. 2C shows the position after knob 13 has been released. In thisposition, ferrule 17 of the plug 25 is physically contacted andoptically connected with the ferrule of the combined optical fiber andferrule component 22. Sleeve 16 covers optical fiber 15 and becomestapered to smoothly guide and receive the ferrule of the component 22.The ferrule 17 is pushed longitudinally forward or toward the ferrule ofthe optical fiber with ferrule component 22 by a spring 14 that holdsthe ferrules together by a force sufficient to achieve the contactpressure required to realize the optical connection.

After the optical connection has been established, the plug can still bereadily detached from the receptacle by pulling back on the knob 13 andguiding it into the knob guidance groove 12. By this action, the sleeve16 is stored completely and fixed in the plug housing 11. Thereafter,the plug housing 11 can be pulled upwardly from the receptacle housing18 to detach the plug 25 from the receptacle 24.

With respect to the embodiment of the present invention, the opticalconnection loss resulting from the detachable structure is within 0.5dB. This optical connection loss does not deteriorate even after 100times of repetitive detachment of the plug 25 and the receptacle 24. Anoptical return loss could be kept greater than −40 dB.

Even if the parts are reversed with respect to the plug and receptaclesides of the module, in which case sleeve 16 would be attached with theoptical fiber and ferrule 22, the aforementioned effect would beobtained. Although the structure of the guidance mechanism attached tothe plug housing 11 and the receptacle housing 18 is shown with a smoothwalled structure, when there is provided a guidance mechanism formeshing each other, the same effect can be obtained. Although theembodiment of the present invention is an example of the opticaltransmission module or optical module, the present invention can be usedas well for the optical connection of optical fibers.

FIG. 3 shows an example circuit diagram of a circuit board having anoptical transmission module or an optical module relating to the presentinvention mounted thereof. Optical transmission modules or opticalmodules 27 and 28 are mounted on a circuit board 26 and optical fibers29 are connected thereto. A plurality of electronic components 30 areplaced on the circuit board 26. Because the optical fibers can bedetached from the receptacles of the modules in the vertical direction,the optical transmission modules or optical modules 27 and 28 relatingto the present invention can have electronic components 30 assembledperipherally around them. Accordingly, the present invention does notrequire a free space along the surface of the circuit board to detachthe optical connector in the conventional manner and it is possible toperform a high density surface mounting on the circuit board. Therefore,a cost reduction in the mounting of the components can be realized.Further, since it is possible to mount the optical transmission moduleor optical module of the invention on the central area of the mountingboard, a board design of a wide range can be made available. Because theconnector portion of the optical transmission module or optical modulehas a configuration that enables the optical fiber to be detached in thevertical direction above the module, the configuration is applicable toan optical transmission module or an optical module having a low heightprofile.

Based on the present invention, an optical transmission module or anoptical module optimum for high density mounting can be acquired.

While a preferred embodiment of the present invention has been describedin detail, with variations and modifications, further embodiments,variations and modifications are contemplated within the broader aspectsof the present invention, in addition to the advantageous details, inaccordance with the spirit and scope of the following claims.

What is claimed is:
 1. An optical transmission module or an opticalmodule, comprising: an optical component package having an opticalcomponent; a receptacle at one end or one side of said optical moduleadjacent said optical component package having an upwardly facing openarea; and a plug connected to a optical fiber that is detachablyconnected to said receptacle by insertion of said plug in a downwardlyextending insertion direction through said upwardly facing open area toseat said plug within said receptacle for optically coupling saidoptical fiber to said optical component.
 2. The optical transmissionmodule or optical module of claim 1, wherein said plug has a housinghaving an outer periphery of a predetermined shape and said upwardlyfacing open area of said receptacle has a configuration that matchessaid predetermined shape of said plug housing.
 3. The opticaltransmission module or optical module of claim 2, wherein saidpredetermined shape of said outer periphery of said plug housing iscross-shaped.
 4. The optical transmission module or optical module ofclaim 1, wherein said optical fiber extends in a direction transverse tosaid insertion direction of said plug and wherein said plug has amechanism that moves said optical fiber toward and away from a positionin which said optical fiber is coupled with said optical component. 5.The optical transmission module or optical module of claim 4, furtherincluding said plug having a first ferrule connected to the opticalfiber, said optical component package having a second ferrule, said plughaving a spring for urging said first ferrule in contact with saidsecond ferrule when said plug is seated within said receptacle, whereinsaid mechanism has a knob to manipulate movement of said first ferruleaway from said second ferrule during insertion and removal of said plugto prevent contact between said first and second ferrules.
 6. An opticalmodule, comprising: an optical component package having an opticalcomponent mounted on a substrate within said optical component package;a receptacle at one end or one side of said optical module having anopen top area, a bottom wall and opposed side walls; a plug connected toan optical fiber that is detachably connected to said receptacle byinsertion of said plug in a direction extending downwardly through saidopen top area from above said receptacle; and an optical coupling fromsaid optical fiber to said optical component passing through said plugand said receptacle in a direction of lightwave propagation that istransverse to said insertion direction.
 7. The optical module of claim6, wherein one of said two side walls is adjacent said optical componentpackage and another of said two side walls is opposed to said one sidewall.
 8. The optical module of claim 6, wherein said bottom wall of saidreceptacle fixes a height of said plug with respect to said receptaclefor aligning said optical coupling.
 9. An optical connector, comprising:a first optical fiber; an optical module having a second optical fiberconnected to an optical component; a receptacle at one end or one sideof said optical module for connecting said first optical fiber to saidoptical module through said one end or one side, said receptacle havingan upwardly facing open area; and a plug having housing in which aferrule is connected to said first optical fiber, wherein said plug isdetachably connected to said receptacle by insertion of said plug in adownwardly extending insertion direction through said upwardly facingopen area to seat said plug within said receptacle for opticallycoupling said first optical fiber to said optical component through saidsecond optical fiber.
 10. The optical connector of claim 9, wherein saidplug has a mechanism including a sleeve that moves with said ferrule andsaid first optical fiber toward and away from a first position in whichsaid first optical fiber is coupled with said optical component.
 11. Theoptical connector of claim 10, wherein said mechanism has a knob tomanipulate the movement of said sleeve with said ferrule and said firstoptical fiber away from said first position during insertion and removalof said plug.
 12. The optical connector of claim 11, wherein saidmechanism further includes a spring for biasing said first optical fibertoward said position and a knob guidance groove formed in said housingof said plug for guiding and holding said knob in a second position awayfrom said first position during insertion and removal of said plug. 13.An optical transmission device, comprising: a plug having a housingstructure including within said housing: a knob, a first ferrule, asleeve, a spring and a knob guidance groove; a first optical fiberconnected to said first ferrule, said sleeve and said knob being fixedto said first ferrule and said spring being positioned between saidhousing and said knob for biasing said first ferrule toward a firstposition; an optical package having a substrate, a second ferrulemounted on said substrate, an optical component mounted on saidsubstrate and a second optical fiber connected to said second ferruleand mounted on said substrate; a receptacle adjacent a side or end ofsaid package; said package having an opening through which said secondferrule is exposed for connection to said first ferrule in said firstposition; said receptacle having an upwardly facing open area; and saidplug being detachably connected to said receptacle by insertion of saidplug in a downwardly extending insertion direction through said upwardlyfacing open area to seat said plug within said receptacle, wherein saidfirst ferrule is moved to and held in a second position with said knobtraveling in said knob guidance groove against the bias of said springfor insertion of said plug, and then returned to said first position foroptically coupling said first and second ferrules.
 14. The opticaltransmission device of claim 13, wherein said first and second opticalfibers and said optical component are aligned in a lightwave propagationdirection on said substrate of said package that is transverse to saiddirection of insertion of said plug.
 15. The optical transmission deviceof claim 14, wherein said knob moves said optical fiber, said sleeve andsaid first ferrule together in the lightwave propagation direction. 16.The optical transmission device of claim 13, wherein said plug housinghas an outer periphery of a predetermined shape and said upwardly facingopen area of said receptacle has a configuration that matches saidpredetermined shape of said plug housing.
 17. The optical transmissiondevice of claim 16, wherein said predetermined shape of said outerperiphery of said plug housing is cross-shaped.